It is difficult to adhere conventional adhesive tape constructions to substrates having rough surfaces without compromising either a strong adhesive bond to the substrate or a smooth, flat appearance of the backing. With most conventional tape constructions application pressure causes the tape backing and adhesive to distort and generally conform to the surface topology of the substrate surface. On removal of this pressure the tape attempts to return to its original undeformed condition because of the elastic and anelastic properties of the backing and the adhesive, thereby creating stresses at the adhesive/backing and adhesive/substrate surface interfaces. When tape constructions having stiff, yet deformable backings are adhered to rough substrate surfaces, the attempt to return to the original, undistorted configuration typically causes an adhesive failure at the adhesive/substrate surface interface as the adhesive is pulled away from the recesses on the substrate surface as the backing returns to a smooth, flat configuration. As a result, the contact area between the adhesive and the substrate can be reduced to the point that the adhesive tape does not adhere to the substrate surface. Tape constructions which utilize softer, readily deformable backings in combination with adhesives that form very strong adhesive bonds to the rough substrate surface are typically unable to return to a smooth, flat configuration as the strength of the adhesive bond is greater than the restorative forces of the backing.
One approach to reducing adhesive failure problems at the adhesive/substrate surface interface involves the use of a thicker layer of a more conformable adhesive than is typically used in conventional tape constructions. However, increasing the adhesive thickness adds cost to the tape and often results in adhesive oozing or flowing out beyond the backing. Adhesive ooz or flow is extremely undesirable when the adhesive construction is a decorative material or wall covering. Adhesive ooz is also a serious problem when a tape construction is formed into a roll for shipping purposes. Finally, if pressure is applied to the backing after the tape is applied to the rough substrate surface, additional adhesive oozing along the edges of the backing can occur.
Yet another attempt to overcome the problem of an adhesive failure at the adhesive/substrate surface interface is to utilize a backing that deforms by plastic deformation, such as an annealed metal foil backing. Backings of this type typically have little, if any restoring forces so that the tape construction will remain conformed to the topology of the rough substrate surface when application forces are removed. However, this solution fails to provide a backing that assumes a substantially smooth and flat configuration after attachment to the rough surface.
Still another attempt to overcome the above-noted problems is to utilize a foam intermediate layer between the backing and the adhesive which allows the adhesive to remain in contact with the substrate surface while the backing can return to a smooth, flat configuration. However, a comparatively thick layer of a compliant foam is required to achieve the desired balance between conformability to the rough surface and allowing the backing of the tape to return to a smooth, flat configuration.